Contemporary hard disk drives include an actuator assembly pivoting through an actuator pivot to position one or more read-write heads, embedded in sliders, each over a rotating disk surface. The data stored on the rotating disk surface is typically arranged in concentric tracks. To access the data of a track, a servo controller first positions the read-write head by electrically stimulating the voice coil motor, which couples through the voice coil and an actuator arm to move a head gimbal assembly in lateral positioning the slider close to the track. Once the read-write head is close to the track, the servo controller typically enters an operational mode known herein as track following. It is during track following mode that the read-write head is used to access the data stored of the track.
Micro-actuators provide a second actuation stage for lateral positioning the read-write head during track following mode. They often use a piezoelectric effect to rapidly make fine position changes. They have doubled the bandwidth of servo controllers and are believed essential for high capacity hard disk drives from hereon. The inventors have found certain problems associated with previous micro-actuators, which has lead them to make this invention's improvements.